"People come because it's the exercise they can do and it makes them feel good," said Gendry, who founded the school in 2004. "It's the easiest form of yoga. They can't twist, they can't bend, but they can do this."

A blend of yogic deep breathing, stretching, and laughter exercises that cultivate child-like playfulness, Laughter Yoga was developed 17 years ago in Mumbai, India by Dr. Madan Kataria. Laughter Yoga International now claims 600 clubs in 60 countries.

Gendry, who was born in France, was the first American to train as a certified Laughter Yoga teacher.

Central to Laughter Yoga is the tenet that the body cannot differentiate between pretend and genuine laughter.

"We fake it," Gendry said of the group classes he leads. "We simulate to stimulate. We go through the motions of joy to create the chemistry of joy."

In one exercise attendees are instructed to repeat "ho-ho, ha-ha-ha" while clapping hands; in another they are directed to "picture yourself jumping for joy."

The exercises are unapologetically silly and very shortâ20 to 40 seconds each in an hour-long class, Gendry said, to facilitate the shift from thinking to feeling.

"The goal is not to work on muscle mass," he said. "It is to overcome critical thinking."

Another goal is to connect with classmates.

"Laughter is a means to an end," he explained. "In hatha yoga (the yoga commonly taught in studios and health clubs), the focus is the breath. In laughter yoga, the focus is the "dristi," or gaze, of the other. It builds community."

It's also easy. Gendry said it usually takes two days to master the fundamentals of the method.

"For those who want to teach, it takes a week," he said. "Truly, this is not rocket science."

New York City-based fitness expert Lashaun Dale, who has been teaching movement, fitness and yoga for over 20 years, said she really enjoyed the Laughter Yoga class she attended.

"It's a hoot," said Dale. "It releases so much stress. You can't help but laugh. First, there's discomfort; then it's hard to stop."

Dale said the class favored gentle, healing movement over the intense stretching and exertion of the vinyasa flow of typical yoga classes.

"It is a way to do movement," she said. "If you're stressed out, you're not taking care of yourself. You can't get fit until you get balanced."

Humor can boost the immune system and lower blood pressure, according to the Centers for Disease Control, and laughing for 10 to 15 minutes a day can burn 10 to 40 calories.

Gregory Chertok, sport psychology counselor and fitness trainer at the Physical Medicine and Rehabilitation Center in Englewood, New Jersey, said there is a staggering amount of documented findings on the importance of mood to behavior.

"It (laughing) is not like doing a cardio workout or a plank (exercise)," said Chertok, who encourages his athlete clients to notice their moods. "It's less of a physical, more of a social, benefit. Engaging with people is an enjoyable thing."

Chertok noted that writer and researcher Norman Cousins, whose book "Anatomy of an Illness" influenced Kataria, famously referred to laughter as "internal jogging."

He said the Self-Determination Theory, a psychological theory of motivation, says that anyone seeking a healthy lifestyle must feel three things: autonomy, competence, and relatedness.

"A person who is not physically able to do more strenuous yoga may feel more competent and related in a setting like this (laughter yoga)," he said.

Of course, as Pandora discovered to her dismay, even openness has consequences.

"You cannot open up your box of emotions separately," Gendry explained. "Laughter and tears go side by side. The more you laugh, the more you cry. You can't avoid that."

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